Means for rapid heating of electrondischarge tube filaments



March 10, 1942. I E. BARTON 2,275,581" MEANS FOR RAPIIS HEATING OF ELECTRON-DISCHARGE TUBE FILAMENTS Filed April 15, 1959 Patented Ma 10, .1942

MEANS FOR RAPID HEATING OF ELECTRON DISCHARGE TUBE FILAMENTS Loy E. Barton, Collingswood, N. J., assignor, by

mesne assignments, vision Corporation, ration of Delaware Application April 13, 1939, Serial No.

In Great Brita-i 9 Claims.

This invention relatesto means for very rapidly heating the filaments of radio tubes whereby an initially cold filament may be quickly heated and rendered electron-emitting in less time than has heretofore been possible.

The principal object of the invention is to provide novel means, which may be electromechanical or electrical, for effecting rapid heating of the filament of a tube.

Another object of the invention is to provide a circuit in which known apparatus may be used to control the energization of the filament of a tube in a novel manner.

Another object of the invention is to provide a novel electrical arrangement wherein the rapid heating of the filament iseffected by storing energy in a condenser by charging it to a moderately high potential, and then rapidly dissipating this energy through the tube filament whereby the latter is quickly heated to its operating temperature. The circuit for charging and discharging the condenser may take one of many forms and may, if desired, include means for maintaining the filament at its rated operating temperature subsequent to said rapid heating.

The invention is particularly applicable in that class of electronic equipment which is used only during short isolated intervals of time, and where it is undesirable to maintain the equipment in operation continuously merely to maintain it in readiness for such discontinuous operation. In such service, however, it may be necessary that when the apparatus is called upon to respond, it do so substantially at once, without the delay occasioned by an appreciable warm-up period. Thus it has been found that even the warm-up time of filament-type battery tubes, while relatively short compared to the warm-up time for heater type tubes, is far too long to meet the demands of certain conditions. As an illustration of the type of service for which the present invention is adapted, reference may be had to the co-pending application of Milton L. Thompson, Serial No. 104,667, July 2'7, 1938, wherein the invention may be employed in the Control signal generator to obtain rapid heating of the oscillator tube.

Accordingly there is provided by the present invention, a space discharge device having a filament, means for applying a voltage to said filament which is higher than the rated operating voltage whereby said filament may be quickly heated to its rated operating temperature, and means for removing said higher voltage 5' to Philco Radio and Tele- Philadelphia, Pa., a corpo- 11 August26, 1938 after a predetermined short time whereby said filament is protected against overheating.

In the accompanying drawing:

Fig. 1 is a diagrammatic embodiment of one form of the invention;

Fig. 2 is a diagrammatic embodimentof a variation of the circuit of Fig. 1;

Fig. 3 is a similar illustration of a further embodiment;

Fig. 4 is a similar illustration "of a variation of Fig. 3; and

Fig. 5 is a further illustration of still another variation of the circuit of Fig. 3. I

In Fig. 1, the filament of tube V is energizable by either of the batteries A and Bthrough the medium of switch S which may have contacts 1 and 2 engageable by a switch arm as illustrated. D may be a manual or other driving means secured to the switch arm so as to rotate the same. In the figure, operation of the switch arm counterclockwise from an inoperative position first results in the momentary application of the high voltage of battery B across the filament when the arm engages contact I. This rapidly heats the filament, but if the contact is only momentary no harm will be done. The switch arm may then engage contact 2 thereby connecting thenormal filament supply A, and thus maintaining the filament at its rated temperature.

In Fig. 2, there isshown a modification in which the switch S1 comprises a group of spaced contacts 3 as shown. D in this case may be a means to rotate the switch arm clockwise at a uniform angular speed. By proper adjustment of the potential of battery B, the speed of rotation of the switch arm, and the diameter and spacing of the contacts 3, the filament may be continuously maintained at or near its operating temperature but below the temperature at which the filament would b destroyed or injured. vIf desired, the speed of rotation of the switch arm and the diameter and spacing of the contacts 3 may be so adjusted that the filament is brought to its operating temperature only intermittently, whereby the triode may be rendered operative once for each contact made by the switch arm. The driving mechanism and switch may take the form of a dial mechanism of the type employed in telephone systems if the tube V is to be in operation for a short period of time, or most any of the common mechanically driven switches could be adapted to the foregoing circults.

In Fig. 3, B is a relatively high voltage plate the type shown in Fig. l.

supply battery of standard type across which may be connected the resistance R and condenser C. The filament of tube V may be connected,

used to heat the filament thereby quickly rendering the tube V operative, butthe filament will not be damaged since the energy thus dissipated will not be suflicient to burn the filament. If switch S2 remains closed, the resistance R may act in conjunction with the resistance .of' the filament to reduce the applied voltage from battery B to its proper value, and in this manner the filament may be kept inoperating. condition as long as may be desired. Thus, in this instance the rapid heating of the filament and the subsequent operation are controlled electrically in response to the closing of the switch.

Fig. 4 is a modification of Fig. 3 in which the switch S1 may be adapted to engage the contacts 3 in the manner of the switch of Fig. 2. In this case, B may be a small current limiting resistor. The operation of switch S1 will cause the charge and discharge of condenser C, and the transfer of energy from condenser C to the tube filament as will be readily understood.

In Fig. 5, there is shown a further modification of the invention wherein the switch S is of In this instance, the condenser C is charged and when the switch is thrown to position I, the filament is heated :as described in connection with Fig. 3. However, in this instance the switch may be thrown to position 2 to disconnect the battery B and connect the battery A for normal operation. If desired, =a suitabledriving means D may be provided to operate the switch as in Figs. 1, 2 and 4.

In the .circuits of Figs. 3 to 5, the capacity of the condenser and the potential to which it is charged will determine the energy supplied to the filament from the condenser. Thus a filament rated for 2 volts and 60 milliamperes might require 0.13 watt second for very rapid heating.

If B is a 90 volt battery and Ca 50 microfarad condenser, this energy will be delivered in approximately 0.0085 second. If R (Figs. 3 and 5) is a 1450 ohm resistor the filament may be heated continuously from the B battery.

In the devices of Figs. 1 and 2, the battery B may be of sufficient voltage to heat the filament to its rated operating temperature in a fraction of a second, and the contact effected by the switch may be of such duration.

Thus there is provided by this invention a means to supply energy to a tube filament at a high rate for a short time and then to supply energy to the filament at the normal rate, whereby the time required to render the filament electron-emitting is reduced to a minimum.

It will be apparent that various other embodiments of the invention are readily possible, those illustrated being only for the purpose of disclosure.

I claim:

1. In an electrical circuit, a vacuum tube having a filament adapted to be heated electrically to a predetermined operating temperature, electrical energy storing means capable of storing a sufficient quantity of electrical energy to heat said filament very rapidly substantially to said temperature, means for storing electrical energy in said storing means, means for applying the denser capable of storing a sufiicient quantity of electrical energy to heat said filament very rapidly substantially to said temperature, a source of voltage of magnitude sufiicient to store the said quantity of energy in said condenser, means connecting said condenser to said source, means for connecting said filament across said condenser to thereby heat the filament very rapidly, and means for thereafter applying to said filament a lower voltage sufiicient to operate said filament at the said temperature.

3. In an electrical circuit, a vacuum tube having a filament adapted to emit electrons when heated to a rated operating temperature by a rated filament current, a series loop circuit comprising a resistor, a condenser, and a voltage source, switching means for connecting said filament across said condenser whereby the charge on said condenser is quickly dissipated in said filament, and means associated with said switching means for thereafter maintaining said filament at its rated operating temperature.

4. In an electrical circuit, a vacuum tube having a filament adapted to emit electrons when heated to a rated operating temperature by a rated filament current, a series loop circuit comprising a resistor, a condenser, and a Voltage source, and switching means for connecting said filament across said condenser whereby the charge on said condenser is quickly dissipated in said filament, the sum of the resistances of said resistor and said filament being substantially equal to the voltage of said voltage source divided by the rated filament current.

5. In combination, a space discharge device having 2. directly heated filamentary cathode, a source of electrical energy, the voltage of said source being considerably greater than the rated voltage of said filamentary cathode, a current limiting resistor having a first terminal connected to one end of said source and a second terminal connected to one end of said cathode, a connection between the other end of said source and the other end of said cathode, said last-named connection including a circuit making-and-breaking means adjusted and arranged to supply current from said source to said filamentary cathode in separate pulses, and a condenser connected between said second terminal of said resistor and the other end of said source.

6. In combination, a space discharge device having a directly heated filamentary cathode, a source of electrical energy, the'voltage of said source being considerably greater than the rated voltage of said filamentary cathode, conductive means connecting one end of said source with one end of said cathode, and a single conductive connection between the other end of said source and the other end of said cathode, said lasthaving a directly heated filamentary cathode, said filamentary cathode having a negligibly small heat storage capacity, a source of electrical energy, the voltage of said source being considerably greater than the rated voltage of said filamentary cathode, conductive means connecting one end of said source with one end of said cathode, and a connection between the other end of said source and the oher end of said cathode, said last-mentioned connection including a circuit making-and-breaking means comprising a series of spaced interconnected contacts, a movable contacting member adapted to contact said spaced contacts in succession, and a driving means coupled to said movable member for eifecting movement of said member over said spaced contacts, the width and spacing of said contacts, and the speed of said movable member being such that said filamentary cathode is brought up to rated operating temperature only intermittently.

8. In combination, a space discharge device having a directly heated filamentary cathode, a source of electrical energy,

condenser for storing a predetermined amount of said energy in an electrostatic field, and means including a switch for rapidly dissipating the energy of said electrostatic field in said filamenmeans including a tary cathode.

9. In combination, a space discharge device having a directly heated filamentary cathode, a source of electrical energy, the voltage of said source being considerably greater than the rated voltage of said filamentary cathode, conductive means connecting one end of said source with one end of said cathode, and a single conductive connection between the other end of said source and the other end of said cathode, said lastnamed connection consisting of a circuit-making and -breaking means adjusted and arranged to supply current from said source to said filamentary cathode in successive pulses of substantially greater than normal voltage, each pulse having a predetermined short duration such that the filament is heated substantially to its operating temperature but is prevented from being excessively heated.

LOY E. BARTON. 

